Precombustion-chamber engine



Nov. 16, 1937. mg; 2,099,31

PREGOMBUS'IIION CHAMBER ENGINE Filed June 24, 1953 3 Sheets-Sheet 1 Nov.,16,' 1937. K. RABE PRECOMBUSTION CHAMBER ENGINE 3 Sheets-Sheet 2 Filed June 24, 1955 Nov. 16, 1937. K. RABE PRECOMBUSTION CHAMBER ENG INE 3 Sheets-Sheet 3 Filed June 24, 1935 fizz v en for ?atented Nov. 16, 1937 UNITED STATES PATENT OFFICE Application June 24,

In Germany This invention relates to an internal combustion engine with a precombustion. chamber and direct injection, wherein the said chamber communicates with the interior of the cylinder 5 through a choke device which oflers a small resistance to the entry of air and a considerable resistance to the exit of the mixture.

It has already been proposed to provide engines of this type, wherein the choke device comprises a plurality of atomizing orifices and one or more flow passages controlled by automatic non-retum valves. This should have the effect that the loss of pressure during the inflow is small, whereas the increase of pressure due to the combustion in the precombustion chamber is substantial, in order that as good an atomization as possible of the rest of the fuel may be'obtained. This choke device suffers from the defect that the proportion of resistance between the inflow and outflow is still too small for obtaining the desired result in full. A further defect is this that the non-return valves are permanently exposed to the high temperatures of combustion, and therefore troubles are experienced in the operation after a very short time.

It has also been proposed to provide engines with a precombustion chamber having an incandescent insert, the end of which, protruding freely into the said chamber forms a kind of intermediate chamber wherein the iuel is injected. This intermediate chamber communicates with the precombustion chamber through a plurality of apertures disposed tangentially to the circumference of the incandescent insert and with the interior of the cylinder through a plurality of vaporizing holes provided in the bottom of the incandescent insert. This is supposed to have the effect that the mixture flowing back from the precombustion chamber is first caused to perform a whirling motion for the purpose of mixing with the rest oi the fuel before entering the cylinder. This arrangement has the defect that the energy freed in the precombustion chamber through the combustion is subjected to two consecutive transformations of pressure into speed, which is accompanied by considerable losses and does not result in a complete vaporization of the fuel. Another defect is this that the incandescent insert which is directly exposed to the high temperatures of combustion has to be replaced quite frequently.

The novelty of the invention consists in this that the choke device comprises a round, or helical whirling chamber which has a central conduit leading to the interior of the cylinder. and a 1933, Serial No. 677,446

June 27, 1932 tangential conduit leading to the precombustion chamber, the fuel being injected into the precombustion chamber or into the choke device preferably coaxially with the central conduit. In this choke device the inflowing fuel the shortest connection of its channels, while the outflow is effected through long helical convolutions round the central conduit, so that an exceedingly high exit resistance-may be obtained while the resistance to entry is small. This has the effect that almost the whole of the energy freed in the precombustion chamber due to the combustion is stored as a pressure energy, is converted into speed energy passes through and may be utilized for I vapourizing the rest of the fuel. In addition, due 1 to the whirling which is efiected with the greatest possible force, a completely uniform fuel mixture is prepared, which assures. complete combustion in the interior of the cylinder. The choke device which is of simple construction and may be cooled as required assured undisturbed operation even at the highest combustion temperatures.

Accordingly, an object of this invention is the provision of an improved arrangement for the passage of the gases of an internal combustion engine between the whirling and precombustion, chambers thereof.

A more specific object of this invention is the provision of an improved internal combustion engine wherein the injected fuel is more efficaciously. vaporized and a completely uniform fuel mixture is prepared.

Still another object of this inventionis the provision of an improved internal combustion engine wherein the passage between the whirling chamber and the precombustion chamber thereof offers a minimum of resistance to the flow of gases from the main combustion chamber to the precombustion chamber, while offering a maximum resistance to flow of the gases from the pre combustion chamber to the whirling chamber.

Other and additional objects and advantages of the present invention, together with desirable details of construction and improved combinations of parts, will ticularly pointed out in the claims.

The device according to the invention is illustrated in the accompanying drawings, wherein several embodiments are cording to construction and operation.

' Fig. 1 is a vertical sectionaldiagrammatic view through the cylinder.

Fig. 2 is a section on the line'2-2 of Fig. 1.

be hereinafter described and par- I shown separately ac- Fig. 2a is a diagram showingthe distribution I 1 9i the speeds of the gases in Fig. 2.

, chamber 3, flows Fig. 3 is a second embodiment in section according to Fig. 1.

Fig. 4 is a third embodiment, being a section In the embodiment shown in Figs. 1 and 2 the precombustion chamber I is disposed transversely and eccentrically to the axis of the cylinder head. It is preferably cast integral with the choke and the cylinder. The choke comprises a fiat round chamber 3, the axis of which is identical with the axis of the cylinder, and two connecting channels of approximately equal area. The channel 2 which is tangential to the circumference of the chamber 3 connects the chamber I with the chamber 3, while the channel 4 disposed centrally in the axis of the chamber 3 connects same with the interior of the cylinder 5. The openings of these channels 2, 4 are rounded off. The injector nozzle 6 is disposed in chamber 3 concentrically with the central channel 4. It injects the fuel in the shape of a closed cone 8 through the chamber 3 into the channel4. The interior of the cylinder is conical. The chambers I, 3 and the channels 2, 4 are surrounded by the cooling water of the cylinder head.

The processes of fiow in this choke device 2, 3, 4 are as followsz-During the upward movement of the piston I the air from the interior of the cylinder 5 passes through channel 4 into therethrough in the direction of the arrow e and finally reaches chamber I through channel 2, where it is stored. In this manner only the 2, 4 and the change direction resistance of chamher 3 is opposed to the fiow so that the drop in pressure is verysmall. Due to the -increase of pressure produced by the combustion in chamher I the mixture leaves through channel 2 in the direction of the arrow 22, its direction is changed by the wall of chamber 3 and it is compelled to whirl in the direction of the arrow (1. This whirling first of all prevents the exit of the mixture from chamber 3 until the lines a of whirling becomeso dense that it can be forced down into the channel 4 from the nucleus of the whirl. In this mannerthe resistance to the fiow is considerably increased. The speed of the lines of whirling a increases from the circumference of chamber 3 towards the centre up to theoretically infinite at the axis of whirling. These speeds u are diagrammatically shown in Fig. 2a

plotted on the radius r of chamber 3. The increase of speed in practice is limited by that the lines a of whirling suddenly lose their guide at the top dge of channel 4 and screw themselves therethrough into the cylinder 5. This process may be compared to the waterspout of a cyclone in which case all particles rotating at the highest speed in the nucleus of whirling are forced to fly out in the axis of the whirling.

The size of the whirl chamber 3 depends on the stroke volume and the number of revoluthe line I Il-I 0 of Fig. 9.

choke resistance of channels,

air from the cylinder 5 into tions of the machine. The height of chamber 3 combustion must be effected, the greater is the required degree of fineness of vaporization and therewith the diameter of chamber 3. The volume of this chamber 3 is therefore predetermined for every engine, it is, however, so small in proportion to the compression volume of the machine that chamber 3 cannot be regarded as an intermediate chamber in the sense of other constructions.

On the other hand the size of the precombustion chamber may be anything within certain limits. It may be made so large that the greater part of the air of combustion is stored therein, or it may be so small that it will only take the air necessary for the combustion in the precombustion chamber. For the distribution of air between the precombustion chamber l and the cylinder 5 the first consideration is the place and form of the injection of the fuel.

preparation thereof. Consequently various processes may be carried into effect with this device, which may be selected according to the application of the engine, the nature of the fuel and therefore economical viewpoints. The distribution of air between chamber I and cylinder 5 depends on the size of For the first method of operation, which forms the basis of the embodiment according to Figs. 1, 2, assume that the greatest part of the combustion air is stored in the chamber I at the end of the compression stroke. The injection begins shortly before the upper dead centre and terminates far behind the same. Due to the flow of chamber I, which due to the inertia of the column of air is continued approximately up to the upper dead centre the first part of the injected fuel is seized and carried on into the chamber I. particles evaporate in the high temperature air,

the combustion. During this delay of ignition the products of decomposition reach the chamber I without fall, so that the combustion under 'inclusion of the oncoming, slightly prepared fuel particles extend in this chamber and not in the whirling chamber 3. Since only a small quantity of fuel is seized by the combustion, this iseffected in excess air, that is to say perfectly and completely. The combustion causes anincrease of pressure in chamber I, due to which the mixture begins to flow out through channel land to whirl in chamber 3. At first it cannot leave through channel 4 due to the great resistance, so that the increase of pressure in chamber I is carried to the highest degree. This, however, also increases the speed it of whirling, the lines a of whirling become dense and the mixture begins to flow through channel 4. In doing this it seizes the oncoming injected fuel particles, causes them to whirl and mixes therewith to a saturated; ignitable mixture that bursts into flame before leaving channel 4. In this condition it is vaporized in the cylinder on leaving channel 4 due to the suddenly-freed kinetic energy and burns in the residual air of the cylinder completely and perfectly. This combustion may be so managed that the combustion air flowing back from chamber I is in the correct mixture proportion to the fuel injected through nozzle 3, so that the two flows, adjusted as regards time and quantity with respect to each other, and meeting in channel 4 assure a continuous combustion. This combustion adapts itself to the continuous increase of the cylinder volume due to the return stroke of the piston in sucha manner that if maximum pressure occurs the back flow and therewith the period of combustion are retarded, while if minimum pressure occurs the back flow and therewith the period of combustion are accelerated. Consequently the combustion takes place at a substantially uniform pressure.

For the second method of operation assume that the combustion air is approximately equally divided between chamber I and cylinder 5. The

injection is effected into the whirling chamber- 3, either in a closed cone directed tangentially to the circumference of chamber 3 opposite to the direction of the lines a of whirling, or in a cone of starlike distribution directed radially to the circumference of chamber 3 and crossing the lines a of whirling. The beginning and the termination. of the injection are approximately equally spaced before and after the upper dead centre. The processes during the combustion in the chamber I, which take .place in an excess of air, are practically the same as in the first method of operation. The rest. of the fuel is subjected to centrifugal action in the returning mixture, that is to say the comparatively heavy fuel particles fly again and again outwards under the action of the centrifugal force, 1. e. to whirling lines lying farther away from channel 4, before they are torn away from the whirling. Not only are they thereby intimately mixed with particles of the mixture but they are prepared to a finished mixture of fuel and air up to the limit of ignitability. This stage must not be reached, in order to avoid premature increase of pressure in the whirling chamber 3, which would stop the flow. The excess air of the chamber I must therefore be accurately determined. Theignition of the fuel mixture thus prepared is only eifected after vaporization in the cylinder 5, where there is plenty of air for saturating this mixture. For this reason the combustion can no longer be continuous. Apart from the back flow it also depends on the vaporization, i. e. on the distribution of the fuel mixture in the residual air of the cylinder 5. For this reason the combustion will be effected as a mixed combustion with moderate increase of pressure.

For the third method of operation assume that chamber I contains only so much air that is absolutely necessary for the combustion. The injection is effected in'the chamber I, no matter injector in what form. It begins so far in front of the upper dead centre that at the beginning of the back flow substantially the whole of the fuel is already introduced. of air, is incomplete and imperfect. It effects the decomposition of the unburnt or only partially burnt residual fuelinto easily ignitableparticles. This fuel mixture cannot be further prepared by the whirling during the back flow, because the combustion air necessary therefor is absent. It is only ignited after vaporization in the ample main air of the cylinder 5. The following combustion depends to the greatest possible extent upon the degree of vaporization of the combustible mixture and only to a small extent on the period 'of back flow. It is therefore effectedwith an increase of pressure which resembles puihng. This method-as compared to the previous ones has the defect that due to the splitting of the fuel in the chamber I"dead combinations are formed, which even with ample excess air in the cylinder 5 can only incompletely burn.

As shown in the embodiment according to Fig. 3,'the central channel 4 is disposed at an angle to the axis of the whirling chamber 3, only its exit lying centrally in chamber 3. This is necessary for reasons of space, either to make the nozzle 6 more accessible, or to be able to dispose the valves in the cylinder head more easily. This embodiment is especially of advantage when the channel 4 is inclined in the direction of the tangential channel. 2. By shortening the line of flow e and reducing its change direction angle the resistance to inflow can be further reduced, while by changing over the nucleus of whirling the resistance to outflow can be further increased, so that a better proportion of resistance in the chokeand therewith an increased degree of vaporization is obtained.

In the embodiment according to Figs. 4 and 5 the chamber I is given an annular form round the whirling chamber 3. The chambers are interconnected by two opposed tangential channels 2, 2'. These channels 2, 2 are formed as comparatively narrow slots in the partition wall IS The combustion, due to lack of chambers I, 3 which reach above the height of chamber 3. The inner edges of these channels 2, 2' are rounded off. The chambers I, 3 are united to a cylindrical vessel 9 which is closed by the lid I2. The central channel 4 lies in a prolongation I0 of vessel 9. Towards the whirling chamber 3 and the cylinder 5 it is rounded off in nozzle formation. The projection I0 is provided with a thread, by means of which the vessel 9 is screwed into the cylinder head I9. The injector nozzle 6 is inserted into a projection I3 of the lid I2 and is secured thereto by bolts. The axis of the whirling chamber is inclined to the axis 0 of the cylinder. The channel 4 opens eccentrically to the piston in a cavity of the cylinder head I9. The piston I approaches the cylinder head I9 up to an unavoidable play. For cooling the vessel 9, the lid is provided with ribs. The vessel is situated in the stream of cooling air in front of the valves 20.

This embodiment offers many advantages. Through the short channels 2, 2' the path of the flow and therewith the resistance to entry in the chamber I is reduced, while the special form of these channels strongly increases the whirling at the outflow and thereby increases the resistance thereto. The chambers I, 3 are insulated from each other through the partition I6, whereby not only are the free surfaces of this device reduced, but part of the heat passing to the wall chambers la, lb is connected to the whirling chamber 3 through 'a tangential channel 2, 2' respectively. The partitions I1, I 'l' are either straight or curved and join the partition l6 tangentially, forming one boundary wall of channels 2, 2. The chambers la, lb may be intercon-v nected by apertures l8, l8 in the partitions l1, l1. These apertures are disposed close'to the wall of vessel 9.

Through this subdivision of the chamber, I the combustion passages for the pre-combustion are siderably supported considerably shortened. The initially injected fuel particles are drawn into these elongated chambers la, lb, without, however, penetrating deeply into the interior thereof, with the result that only the front part of channels 2, 2 that is the part turned towards the chambers la, lb is filled with ignitable mixture, while the rear part turned away from the channels 2, 2 contains substantially pure air. The combustion of this comparatively small quantity of mixture may therefore be effected much quicker than-in the case where this mixture whirls in one continous chamber. The apertures between the part chambers la, lb have the effect that the increase of pressure and therewith the back flow are parallel. If, for example, the ignition begins earlier in one chamber than in the other, then due to the pressure a small part of the combustion air passes over from the air portion of one chamber into the mixture portion of the other chamber and accelerates therein the slow ignition. Through the special form and arrangement of the partitions l1, II the conversion of the pressure energy into speed energy can be conduring the back flow. These partitions l1, l1 serve to turn the mixture flowing from the elongated chambers l a, lb, whereby harmful whirling is prevented. Since these partitions l1, II also form one boundary wall of the channels 2, 2, they may cooperate with partition l6 forming the other boundary wall in such a manner that the outflowing mixture is not only turned but is also accelerated. As especially shown in Fig. 7, ejector nozzles tapering in the direction of the flow may replace the simple channels 2, 2', wherein the conversion of energy may take place free of shocks and whirls, that is to say with the smallest possible losses.

In the embodiment shown in Figs. 8 and 10, the vessel 9 is located in a pocket 1a of the piston bottom. The pro-combustion chamber is arranged in annular form round the whirling chamber 3 and is subdivided by partitions l1, l1, l1" into three chambers I, l', l", whichare connected to the whirling chambers through tangential channels 2, 2', 2" and are interconnected by apertures l8, l9, IS", The slot shaped channels 2, 2, 2" are bounded on the one hand by the partitions l1, l1, l1" and on the other hand by the thickened ends of the partition IS. The vessel 9 is closed by a circular plate l2, which at l2a. is threaded into the piston and is located in a de pression in the piston bottom. The plate I2 is provided with a projection protruding into the cylinder 5 into which the channel 4 opens. The latter is widened towards the cylinder 5 more 2,099,818 "of the vessel is again admitted to the mixture.

than towards the whirling chamber 3. The injector nozzle is inserted into the cylinder head between the valves 20, 20' and lies opposite the projection Ill. The axis 0 of the cylinder, the axis a of the vessel 9 and the axis d of injection coincide. The fuel is injected in the shape of a slim closed hollow cone 8 into the channel 4 in such a manner that the fuel particles pass quite close to the wall of the channel. For this purpose the injector nozzle is provided with a pin.

This special form of injection is effected for two reasons. First, it is to be avoided that the later injected fuel which takes no part in the precombustion is clumped together in the nucleus of whirling and there forms a kind of reserve from which the whirling is fed. Second, a better preparation of the fuel particles is obtained in that they are introduced into such a zone of the back flow which possesses the greatest kinetic energy and at the same time is located near to the place of vaporization. This zone is situated at about the smallest area of channel 4. As the flow diagram in Fig. 11 shows the back flowing mixture sticks to some extent to the wall of channel 4 in the form of a densifled sleeve, which surrounds a thinned nucleus of D" diameter and is reduced from the whirling chamber 3 towards the cylinder 5, that is from 0 towards b in accordance with the diameters D and D' of channel 4. This sleeve is therefore turned fa'n shape due to the form of channel 4 and is vaporized at the prolongation It almost horizontally in the cylinder 5. If new the hollow spray cone touches the circumference of channel 4 at the narrowest point at D without penetrating into the nucleus at D", then the penetration power of the fuel particles is fully braked at this point and the same are ground by the almost horizontally rotating whirl of the mixture particles, as if in a mill.

The injection nozzle 6 must be brought very near to the projection III in order to avoid that fuel particles split ofl. during the injection reach the cylinder from the hollow cone 9 and cause a pre-combustion therein which would counteract that occurring in the chamber I. In order however that the mixture during the outflow may reach the cylinder 5 from channel 4 without being choked, it is necessary that the slot. surface determined by the height it between nozzle 6 and projection l-ll should be adapted to the outlet area D of channel 4. The projection 10 penetrating freely into the cylinder 5 prevents mixture particles from sticking to the outlet of channel 4. Once these particles are separated from cover I 2, they fly due to the twist approximately horizontally and tangentially outwards. Cover l2 and piston 1 must have therefore no projecting parts whereat themixture particles would strike and precipitate. When the cover l2 of the vessel a is arranged in the same plane with the top of the piston 'l, the rotation of the combustion gases may be transmitted freely to the rest of the air in the cylinder chamber 5 and thereby a whirling motion may be maintained which is favorable for the final combustion. AC

The transfer of the injector nozzle 6 into a part spaced apart from vessel '9 has many advantages. The rest of the injected jl'uel may be fed to the mixture in a counterstream instead of in a parallel stream, which favours the preparation. Through avoiding the nucleus of whirling the injection diagram remains unchanged, since the mixture rotating in chamber 3 is not rubbed" on the hollow cone 8. The vessel 9 itself'may be formed in a simplified manner in the shape of a the injector nozzle does not have to be considered.

. In the embodiment shown in Figs. 9 and 10, the vessel 9 is disposed in the bottom of the cylinder head l9. The axis g of the vessel 9 is parallel and at the same time eccentrically disposed to. the axis 0 of the cylinder, so that the bottom of the vessel 9 is level with the cylinder head ill but is oflfset to outside of the diameter of the cylinder. The inje'ctor nozzle 6 is inserted slantingly from below sideways into the cylinder. The channel 4 is formed coaxially therewith in the projection I0,

that is slantingly to the chamber 3. The vessel 9 is closed from outside through the aid of flange 9a. by means of plate l2. The plate I! is screwed on to an annular projection 19a of the cylinder head I9 at l2a. 'It is provided with annular ribs l5 which are cooled by the cooling water of the cylinder head I9.

In this construction the residual air of the cylinder 5 collects round the outlet of channel 4 in a cavity formed by piston I and the cylinder, whereby the post-combustion is favoured. The position of the spray cone 8 with respect to channel 4 is not influenced here by the movements of the piston. The mixture flowing out of channel' l is'vaporized mainly towards piston I, because the guiding ofiered by the walls of the channel in this direction is first lost. Thereby the striking of the stationary wall of the cavity by the mixture is avoided. The vessel 9 is considerably cooled on one side by the cover 12. This is necessary in 7 order to protect the projection III which becomes considerations of space,

incandescent from burning away.

The invention is not limited to these embodiments. The position of chamber 3, i. e. of vessel 9 with respect to the cylinder 5 may be altered according to the construction of the engine and and the same may be located not only in the cylinder head or in *the piston, but also in the cylinder itself. Furthermore it is not necessary to provide one whirling chamber of vessel only per cylinder, since with larger cylinders two or more thereof may be disposed in juxtaposition. It is also possible to provide combined arrangements; e. g. one precombustion chamber with several whirling chambers, or one whirling chamber which in addition to the precombustion chamber also cooperates with air chambers. The may also be varied at will, provided the required injection diagram is adapted to the flow conditions for carrying into effect this or the other method of operation. Instead of one injector nozzle, two may be employed, one of which injects into the precombustion chamber and the other into the whirling chamber. All these variations have the object of utilizing better the advantage of one or the other of the processes,

i. e. to combine the advantages of the various processes. The basic idea of the invention is not altered thereby in any way.

It will be seen that I have provided a construction which satisfies the objects enumerated above and one which constitutes a valuable advance in the art. Willie I have shown the ina box is much more easilyposition of the injector nozzle vention in certain physical embodiments, it is to be understood that modifications of the structure shown may be made by those skilled in this art without departing from my invention as expressed in the claims which follow. a

I claim:

1. In an internal combustion engine, a cylinder comprising a combustion chamber, a precombustion chamber' and an intermediate whirling chamber, said whirling chamber being of genorally round form, having a generally flat top and bottom connected by an .annular side wall and formed with a generally axial passage extending from near the center of one of said generally flat walls in a direction generally transverse to the generally flat top and'bottomof the whirling chamber and into the combustion chamber and provided with at least one passage tangential to the side wall of said intermediate chamber and connecting with the precombustion chamber, whereby during-compression air may flow from the combustion chamber through the intermediate chamber to the precombustion chamber with relatively low. resistance but return flow will cause whirling in the intermediate chamber about its axis and in said passage from the intermediate chamber to the combustion chamber, and a fuel supply device for injecting a charge of fuel into said air for mixing therewith within said precombustion chamber or said intermediate chamber or said passages,

2. An internal combustion engine according to claim 1 in which the fuel supply device consists of a fuel injector nozzle arranged to inject a charge of fuel coaxialiy'with the passage from the intermediate chamber to the combustion chamber and directly into said combustion chamber.

3. An internal combustion engine according to claim 1 in which the fuel supply device consists of a. fuel injector nozzle arranged to inject the fuel jet in a straight unobstructed path through the passage connecting the'combustion chamber with the intermediate chamber.

4. An internal combustion engine according to claim 1 in which the precombustion chamber at least partly surrounds the whirling chamber.

5. An internal combustion engine according to claim 1 in which the precombustion chamber is circularly arranged around the whirling chamber and communicates therewith by a plurality of passages arranged tangentially to the whining chamber and to the precombustlon chamber.

6. An internal combustion engine according to claim 1. in which the precombustion chamber surrounds the whirling chamber and is divided into two parts by partitions and in which each individual part of the chamber is provided with a passage leading to the whirling chamber.

7. An internal combustion engine according to claim 1 in which the precombustlon chamber surrounds the whirling chamber and is divided into two parts by partitions and in which each individual part of the chamber is provided with a passage leading to the whirling chamber and arranged tangentially to the whirling chamber.

8. An internal combustion engine according to claim 1 in which the precombustion chamber surrounds the whirling chamber and is divided into two parts by partitions and in which each individual part of the chamber is provided with ber are integrally connected as a unit and are arranged in a depression in the top 01 the piston.

12. An internal combustion engine according to claim 1 in which the precombustion chamber and the whirling chamber are integrally connected .as a unit and are arranged in a depression in the cylinder head.

13. An internal combustion engine according to claim 1 in which a piston is provided and the precombustion chamber and the whirling chamber are integrally connected as a unit and are arranged in a depression in the top 01 the piston, and the unit is flush with the top surface 01 the piston.

14. An internal combustion engine according to claim 1 in which the precombustion chamber and the whirling chamber are integrally connected as a unit and are arranged in a depression in the cylinder head, and the unit is flush with the surface of the cylinder head wall.

KARL BABE. 

